Deflection Gauges (mandrels) are used to test flexible sewer pipe for out-of-roundness or deflection per ASTM specifications D3034 and F679. This testing ensures that flexible pipe has been properly bedded and backfilled (ASTM D2321) to give optimal performance. Other gauges can get hung up causing a deflection test to fail, even though the pipe is within tolerance. Sized to 0.01 in, steel deflection gauge styles meet ASTM requirements.